1. Field of the Invention
This invention relates to a device for fixing adjacent vertebrae to each other using a rod and unique hollow screws.
2. Description of the Related Art
Fixation (or fusion) of vertebral columns with bone material or rods and plates is a common, long practiced surgical method for treating a variety of conditions. Many of the existing procedures involve components that protrude outwardly that may contact and damage a body part, such as the aorta, the vena cava, the sympathetic nerves, the intestine and the ureter. Also, many constructions involve components that may loosen and cause undesirable problems. A Dunn device was on the market until pulled by the U.S. Food & Drug Administration because of problems with delayed rupture of the aorta secondary to the device being so bulky as to contact the aorta, erode its surface and lead to fatal hemorrhage in several cases.
U.S. Pat. No. 5,152,303 issued to Allen on Oct. 6, 1992 relates to an anterolateral spinal fixation system including a cannulated screw threaded into a vertebra and a rod attached to the screw. The process involves threading the cannulated screw into a pilot hole drilled into the vertebral body portion and fastening a rod at its lower and upper ends to the vertebral body by the cannulated screws. (Col. 3, lines 62-64; Col. 4, lines 5-8).
U.S. Pat. No. 4,059,115 issued to Jumashev et al. on Nov. 22, 1977 relates to a surgical instrument for operation of anterior fenestrated spondylodesis in vertebral osteochondrosis. The instrument includes a hollow cylindrical cutter with a cutting edge, and a handle. By rotation of the handle accompanied with slight pressure the cutter is worked into the bodies of the adjacent vertebras (abstract, Col. 6, lines 56-58).
U.S. Pat. No. 5,015,247 issued to Michelson on May 14, 1991 relates to a method of performing internal stabilization of a spine. The method involves seating a drill sleeve into the two vertebrae and drilling the vertebrae with the drill installed through the drill sleeve. Bagby U.S. Pat. No. 4,501,269 is mentioned. (Col. 6, lines 27-30, Col. 7, line 68, Col. 9, lines 22-25, 39).
Current devices have substantial deficiencies when osteoporotic bone is encountered. The soft, decalcified bone in such patients has poor pull-out strength for screws. Bone screws are known to have very little holding power in osteoporotic bone and loosen readily, severely limiting the holding power and fixation ability of current devices.
Some devices have designs that include hollow screws or screws with transversely drilled holes, presumably to improve holding power and allow bone to grow therethrough. These devices are all relatively small screws which are not capable of large surface area fixation.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. .sctn.1.56(a) exists.